We have been studying autoimmune encephalomyelitis (EAE) in juvenile guinea pigs whih undergo a chronic stage after the acute phase. Monoclonal anti-guinea pig T cells were used to trace T lymphocytes to CNS sites. We are now using such monoclonals to separate and characterize the T cells from guinea pig spleens, lymph node and peritoneal exudate using plating, panning and cell sorter to isolate populations. The significance of the project lies in the opportunity to use monoclonal antibodies (developed at NIAID by Dr. Shevach in mice against surface antigens of lymphocytes of guinea pigs) to identify subpopulations responsible for tuberculin reactivity and induction of autoimmune diseases. First, by panning and cell-mediated lysis, we showed that T cells and not B cells were involved in the induction of guinea pig EAE, just as in mice and rats. Although the antigens cannot yet be characterized, we used a two-color system in cell sorter analysis and two different monoclonal mouse anti-guinea pig T cell antibodies to isolate subpopulations tagged by one or the other of them. One subpopulation induced EAE in histocompatible recipients after purification by cell-mediated lysis using monoclonal antibodies and rabbit complement to remove inactive subpopulations from the T cell population.